An engine discharges thermal energy while generating torque based on combustion of a fuel, and a coolant absorbs thermal energy while circulating through an engine, a heater, and a radiator, and releases the thermal energy to an outside.
When a temperature of the coolant of the engine is low, viscosity of oil may increase to increase frictional force and fuel consumption, and a temperature of an exhaust gas may increase gradually to lengthen a time for a catalyst to be activated which degrades quality of the exhaust gas. In addition, as a time required for a function of the heater to be normalized is increased, a driver may be discomfort.
When the coolant temperature is excessively high, since knocking occurs, performance of the engine may deteriorate by adjusting ignition timing in order to suppress the knocking, when a temperature of lubricant is excessively high, a viscosity is lowered such that a lubrication performance may be deteriorated.
Therefore, a technology to control several cooling elements through one valve unit, such as keeping the high temperature of the coolant for a certain part of the engine and keeping the low temperature of the coolant for other part low is applied.
As an example of a conventional art, the coolant control valve unit includes a motor, a cam rotated by the motor, a rod moved by a track formed at one surface of the cam, and a valve formed on the rod and has a structure opening and closing a coolant passage through the valve if the cam is rotated by the motor and the track of the cam pushes the rod. Friction occurs between the cam and the valve rod, which causes wear on the relatively low-strength valve rod when the valve is operated for a longer period of time. Wear of the valve rod shortens the length of the valve rod to change an opening height when the valve is fully opened, and also changes an angle of the cam from which the valve starts to open. Therefore, in the process of controlling the flow rate of the coolant to the target temperature, it is difficult to precisely control the flow rate of the coolant, so that it may be difficult to control the coolant temperature.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.